ata_piix: disallow UDMA 133 on ICH5 & ICH7

ata_piix: disallow UDMA 133 on ICH5 & ICH7

There is another outstanding issue with ata_piix.c.  Intel has never
officially supported anything faster than PATA 100MB/s.

But, the ata_piix.c driver "define" the ICH5 & ICH7 as UDMA6 (aka 133MB/s)
capable.  [ Well, no one has probably noticed it before, because there is bug
in do_pata_set_dmamode...  Just look at
libata_atapiix_enable_real_udma133.patch and you'll see what wrong with it.  ]

Here are Intel's datasheets for the affected chipsets: ICH5 Datasheet:
http://www.intel.com/design/chipsets/datashts/252516.htm (See note on page
183: "...  the ICH5 supports reads at the maximum rate of 100MB/s.")

ICH7 Datasheet: http://www.intel.com/design/chipsets/datashts/307013.htm (See
first note on page 190: "...  the ICH7 supports reads at the maximum rate of
100MB/s.")

They are two different ways to deal with it:

- Either -

1. replace all ich_pata_133 with ich_pata_100.
   (libata_atapiix_disable_udma6.diff - diff from 2.6.22 )

- Or -

2. keep all ich_pata_133 and fix the bug in "do_pata_set_dmamode".
   (libata_atapiix_enable_real_udma133.patch - diff from 2.6.22) If there are
   any concerns about the safety of the patch patch:
   http://lkml.org/lkml/2007/7/6/292 (It was already tested by an Intel
   employee, but I guess a bit more user input is necessary here...  )

This patch implements 1.

Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Jeff Garzik <jeff@garzik.org>
Cc: Tejun Heo <htejun@gmail.com>
Signed-off-by: Christian Lamparter <chunkeey@web.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>